Semiconductor light emitting device, its manufacturing method, semiconductor device and its manufacturing method

ABSTRACT

A semiconductor light emitting device made of nitride III-V compound semiconductors includes an active layer made of a first nitride III-V compound semiconductor containing In and Ga, such as InGaN; an intermediate layer made of a second nitride III-V compound semiconductor containing In and Ga and different from the first nitride III-V compound semiconductor, such as InGaN; and a cap layer made of a third nitride III-V compound semiconductor containing Al and Ga, such as p-type AlGaN, which are deposited in sequential contact.

RELATED APPLICATION

This application is a continuation of PCT Application No. PCT/JP01/11536filed Dec. 27, 2001, which claims priority to Japanese applications Nos.P2000-401998 filed Dec. 28, 2000, and P2001-271947 filed Sep. 7, 2001,all of which are incorporated herein by reference to the extentpermitted by law.

BACKGROUND OF THE INVENTION

This invention relates to a semiconductor light emitting device and amanufacturing method thereof, as well as a semiconductor device and amanufacturing method thereof, especially suitable for applications tosemiconductor lasers, light emitting diodes or electron transportingdevices made by using nitride III-V compound semiconductors.

Semiconductor lasers made of AlGaInN or other nitride III-V compoundsemiconductors are under active researches and developments assemiconductor lasers capable of emitting light from the blue region tothe ultraviolet region required for enhancing the density of opticaldiscs.

Japanese Patents No. 2780691 and 2735057 disclose semiconductor lasersusing nitride III-V compound semiconductors. A semiconductor laserdisclosed by the former patent is made of nitride semiconductorscontaining In and Ga, and includes an active layer of a quantum wellstructure having first and second surfaces, an n-type nitridesemiconductor layer made of In_(x)Ga_(1-x)N (0≦x<1) in contact with thefirst surface of the active layer, and a p-type nitride semiconductorlayer made of Al_(y)Ga_(1-y)N (0<y<1) in contact with the second surfaceof the active layer. A semiconductor laser disclosed by the latterpatent is made of nitride semiconductors containing In and Ga, andincludes an active layer having first and second surfaces, a p-typecontact layer made of p-type GaN adjacent the second surface of theactive layer, and a first p-type clad layer made of a p-type nitridesemiconductor containing In and Ga between the second surface of theactive layer and the p-type contact layer and having a band gap energylarger than that of the active layer such that the first p-type cladlayer is in direct contact with the second surface of the active layer.

When the Inventor actually fabricated a semiconductor laser using thetechnique disclosed by the former Japanese Patent No. 2780691 for theresearch purposes, the laser exhibited a high initial deterioration ratein its life test and a tendency of gradually increasing in operationcurrent with time. Additionally, remarkably uneven electroluminescentemission of light was observed.

A semiconductor laser experimentally fabricated by using the techniquedisclosed by the latter Japanese Patent No. 2735057 exhibited a stillremarkable increase of the initial deterioration rate.

It is therefore an object of the invention to provide a semiconductordevice made of nitride III-V compound semiconductors, having asufficiently low initial deterioration rate and a long lifetime, andremarkably reduced in change with time of the operation current and inemission unevenness, as well as a method capable of easily manufacturingsuch a semiconductor light emitting device.

More generally, an object of the invention is to provide a semiconductordevice made of nitride III-V compound semiconductors, elongated inlifetime and remarkably reduced in change with time, as well as a methodcapable of easily manufacturing such a semiconductor device.

A further object of the invention is to provide a semiconductor lightemitting device made of nitride III-V compound semiconductors, elongatedin lifetime by improvement of the crystalline quality of its opticalwaveguide layer, additionally exhibiting high symmetry of intensitydistribution of light in far-field images especially in case of asemiconductor laser, and capable of reducing the aspect ratio of theradiation angle (beam divergence angle), as well as a method capable ofeasily manufacturing such a semiconductor light emitting device.

More generally, the further object of the invention is to provide asemiconductor device made of nitride III-V compound semiconductors,elongated in lifetime and having favorable properties, as well as amethod capable of easily manufacturing such a semiconductor device.

SUMMARY OF THE INVENTION

To solve the above-discussed problems, the Inventor made researches withall efforts. Outline thereof is explained below.

For manufacturing a semiconductor laser using nitride III-V compoundsemiconductors, in general, for the purpose of preventing deteriorationof its active layer by elimination of In or preventing overflow ofelectrons injected into the active layer in the process of growing ap-type optical guide layer or a p-type clad layer on the active layer ofInGaN, or the like, at a high growth temperature around 1000° C., theactive layer is first grown, then an approximately 20 nm thick cap layerof p-type AlGaN having Al composition as high as approximately 0.2 isnext grown at the same temperature as the active layer, and a p-typeoptical guide layer ad a p-type clad layer are grown at a raised growthtemperature. However, according to the knowledge of the Inventor,although this structure certainly prevents deterioration of the activelayer by elimination of In, a large difference in lattice constantbetween the cap layer and the active layer causes generation of a largestress in the active layer in contact with the cap layer, and thisinvites deterioration of the active layer. Furthermore, although Mg istypically used as the p-type dopant of p-type layers, diffusion of Mgfrom the p-type layers into the active layer also causes deteriorationof the active layer.

Through various experiments, the Inventor has found that these problemscan be overcome simultaneously by interposing a nitride III-V compoundsemiconductor layer containing In and Ga, such as InGaN, between theactive layer and the cap layer.

After further researches, the Inventor has also found that, in case anitride III-V compound semiconductor containing In, such as InGaN, isgrown while the flow rate of In source material is maintained in thesame level after growth of the uppermost barrier layer of the activelayer having a multi-quantum well structure, quantity of In can beadequately controlled at the growth temperature. Thus, by using it upongrowing such a nitride III-V compound semiconductor containing In, suchas InGaN, since the growth temperature can be raised during the growthand the cap layer can therefore be grown at a raised growth temperatureto improve the crystalline quality, the cap layer can be reduced inthickness or can be even omitted in the ultimate case exclusively fromthe viewpoint of preventing elimination of In from the active layer.

On the other hand, as to the position where the cap layer should belocated in the laser structure, namely between the active layer and thep-type clad layer, there still remains room for improvement. Under thesituation, the Inventor made efforts to optimize the position of the caplayer while taking account of assuring design choice, and has found someoptimum positions from the viewpoints of improving the crystallinequality of the optical guide layer and improving symmetry of intensitydistribution of light in far-field images. Furthermore, the Inventor hasfound various advantages when the aforementioned nitride III-V compoundsemiconductor layer containing In and Ga, such as InGaN, is provided incontact with the active layer in addition to optimizing the position ofthe cap layer.

Although these expedients were confirmed to be effective insemiconductor lasers, they must be effective for all semiconductordevices including light emitting diodes and electron transportingdevices such as transistors as far as they have similar layerstructures.

The present invention has been accomplished as a result of furtherresearches progressed by the Inventor from the above-explainedknowledge.

That is, according to the first of the invention to solve theabove-indicated issues, there is provided a semiconductor light emittingdevice comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

an intermediate layer in contact with the active layer and made of asecond nitride III-V compound semiconductor containing In and Ga anddifferent from the first nitride III-V compound semiconductor; and

a cap layer in contact with the intermediate layer and made of a thirdnitride III-V compound semiconductor containing Al and Ga.

According to the second aspect of the invention, there is provided asemiconductor light emitting device comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

an intermediate layer in contact with the active layer and made of asecond nitride III-V compound semiconductor containing In and Ga anddifferent from the first nitride III-V compound semiconductor; and

a cap layer in contact with the intermediate layer and made of a fifthnitride III-V compound semiconductor containing Ga to be used as anoptical guide layer or a clad layer.

According to the third aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; and a cap layer in contact with the intermediate layerand made of a third nitride III-V compound semiconductor containing Aland Ga, comprising:

growing the intermediate layer while raising the growth temperatureafter growing the active layer.

According to the fourth aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; and a cap layer in contact with the intermediate layerand made of a fifth nitride III-V compound semiconductor containing Gato be used as an optical guide layer or a clad layer, comprising:

growing the intermediate layer while raising the growth temperatureafter growing the active layer.

According to the fifth aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

an intermediate layer in contact with the layer made of the firstnitride III-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; and

a cap layer in contact with the intermediate layer and made of a thirdnitride III-V compound semiconductor containing Al and Ga.

According to the sixth aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

an intermediate layer in contact with the layer made of the firstnitride III-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; and

a p-type layer in contact with the intermediate layer and made of athird nitride III-V compound semiconductor containing Al and Ga.

According to the seventh aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; and a cap layer in contact withthe intermediate layer and made of a third nitride III-V compoundsemiconductor containing Al and Ga, comprising:

growing the intermediate layer while raising the growth temperatureafter growing the layer made of the first nitride III-V compoundsemiconductor.

According to the eighth aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; and a p-type layer in contact withthe intermediate layer and made of a third nitride III-V compoundsemiconductor containing Al and Ga, comprising:

growing the intermediate layer while raising the growth temperatureafter growing the layer made of the first nitride III-V compoundsemiconductor.

In the present invention, the fist nitride III-V compound semiconductorcontaining In and Ga as well as the second nitride III-V compoundsemiconductor may additionally contain Al or B, for example, as a groupIII element other than In and Ga, and may contain As or P as a group Velement. The third nitride III-V compound semiconductor containing Aland Ga may contain In or B, for example, as a group III element otherthan Al and Ga, and may contain As or P as a group V element. The fourthnitride III-V compound semiconductor containing Ga as well as the fifthnitride III-V compound semiconductor may contain In, Al or B, forexample, as a group III other than Ga, and may contain As or P, forexample, as a group V element.

The second nitride III-V compound semiconductor composing theintermediate layer is typically In_(x)Ga_(1-x)N (where 0≦x<1). Theintermediate layer is typically undoped, and normally of an n-type. Thethird III-V compound semiconductor composing the cap layer is typicallyAl_(y)Ga_(1-y)N (where 0≦y<1). Thickness of the cap layer is preferablyequal to or more than 2 nm to ensure a sufficient effect by the use ofthe cap layer. However, if the cap layer is excessively thick, thecrystalline quality deteriorates in some kinds of composition. Toprevent it, thickness of the cap layer is preferably limited not toexceed 10 nm. When the device includes the p-type layer in contact withthe cap layer and made of the fourth nitride III-V compoundsemiconductor, the fourth III-V compound semiconductor composing thep-type layer may be, for example, GaN or In_(z)Ga_(1-z)N (where 0≦z<1).

The active layer made of the first nitride III-V compound semiconductor,or the layer made of the first nitride III-V compound semiconductor,typically has a multi-quantum well structure including well layers andbarrier layers. In this case, composition of In in the intermediatelayer is equal to or smaller than the In composition of the barrierlayers. Various kinds of distribution of the In composition areacceptable. If the intermediate layer is grown while the growthtemperature is gradually raised, the intermediate layer can be formed togradually decrease in composition of In toward its portion remotest fromthe active layer or the layer made of the first nitride III-V compoundsemiconductor. Quantity of In contained in the intermediate layer istypically equal to or less than 5×10¹⁹ cm⁻³. Thickness of theintermediate layer is determined such that the intermediate layer caneffectively prevent deterioration of the active layer or the layer madeof the first nitride III-V compound semiconductor, in accordance withits composition selected. Typically, the thickness is controlled to beequal to or more than 8 nm, and preferably to be equal to or more than10 nm.

The p-type layer composed of the fourth nitride III-V compoundsemiconductor typically contains a quantity of In controlled in therange not less than 1×10¹⁷ cm⁻³ and not more than 5×10¹⁹ cm⁻³.

Any of various kinds of substrates may be used to grow the nitride III-Vcompound semiconductors thereon. For example, a sapphire substrate, SiCsubstrate, Si substrate, GaAs substrate, GaP substrate, GaP substrate,InP substrate, spinel substrate or silicon oxide substrate may be used.A substrate in form of a thick GaN layer or other nitride III-V compoundsemiconductor can be used as well.

For growth of the nitride III-V compound semiconductors, any appropriatetechnique such as metal organic chemical vapor deposition (MOCVD),hydride vapor phase epitaxial growth or halide vapor phase epitaxialgrowth (HVPE), for example, may be used.

The semiconductor device may be a light emitting device such as asemiconductor laser or a light emitting diode, or an electrontransporting device such as FET or a heterojunction bipolar transistor.

According to the ninth aspect of the invention, there is provided asemiconductor light emitting device comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

an optical guide layer in contact with the active layer and made of asixth nitride III-V compound semiconductor containing Ga;

a cap layer in contact with the intermediate layer and made of a thirdnitride III-V compound semiconductor containing Al and Ga; and

a p-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 10th aspect of the invention, there is provided asemiconductor light emitting device comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

an intermediate layer in contact with the active layer and made of asecond nitride III-V compound semiconductor containing In and Ga anddifferent from the first nitride III-V compound semiconductor;

an optical guide layer in contact with the intermediate layer and madeof a sixth nitride III-V compound semiconductor containing Ga;

a cap layer in contact with the optical guide layer and made of a thirdnitride III-V compound semiconductor containing Al and Ga; and

a p-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 11th aspect of the invention, there is provided asemiconductor light emitting device comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

a first optical guide layer in contact with the active layer and made ofan eighth nitride III-V compound semiconductor containing Ga;

a cap layer in contact with the first optical guide layer and made of athird nitride III-V compound semiconductor containing Al and Ga;

a second optical guide layer in contact with the cap layer and made of aninth nitride III-V compound semiconductor containing Ga; and

a p-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 12th aspect of the invention, there is provided asemiconductor light emitting device comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

an intermediate layer in contact with the active layer and made of asecond nitride III-V compound semiconductor containing In and Ga anddifferent from the first nitride III-V compound semiconductor;

a first optical guide layer in contact with the intermediate layer andmade of an eighth nitride III-V compound semiconductor containing Ga;

a cap layer in contact with the first optical guide layer and made of athird nitride III-V compound semiconductor containing Al and Ga;

a second optical guide layer in contact with the cap layer and made of aninth nitride III-V compound semiconductor containing Ga; and

a p-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 13th aspect of the invention, there is provided asemiconductor light emitting device comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

a first optical guide layer in contact with the active layer and made ofan eighth nitride III-V compound semiconductor containing Ga;

a cap layer in contact with the first optical guide layer and having asuperlattice structure in which barrier layers are made of a thirdnitride III-V compound semiconductor containing Al and Ga;

a second optical guide layer in contact with the cap layer and made of aninth nitride III-V compound semiconductor containing Ga; and

a p-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 14th aspect of the invention, there is provided asemiconductor light emitting device comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

an intermediate layer in contact with the active layer and made of asecond nitride III-V compound semiconductor containing In and Ga anddifferent from the first nitride III-V compound semiconductor;

a first optical guide layer in contact with the intermediate layer andmade of an eighth nitride III-V compound semiconductor containing Ga;

a cap layer in contact with the first optical guide layer and having asuperlattice structure in which barrier layers are made of a thirdnitride III-V compound semiconductor containing Al and Ga;

a second optical guide layer in contact with the cap layer and made of aninth nitride III-V compound semiconductor containing Ga; and

a p-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 15th aspect of the invention, there is provided asemiconductor light emitting device comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

an optical guide layer in contact with the active layer and made of asixth nitride III-V compound semiconductor containing Ga;

a cap layer in contact with the optical guide layer and having asuperlattice structure in which barrier layers are made of a thirdnitride III-V compound semiconductor containing Al and Ga; and

a p-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 16th aspect of the invention, there is provided asemiconductor light emitting device comprising:

an active layer made of a first nitride III-V compound semiconductorcontaining In and Ga;

an intermediate layer in contact with the active layer and made of asecond nitride III-V compound semiconductor containing In and Ga anddifferent from the first nitride III-V compound semiconductor;

an optical guide layer in contact with the intermediate layer and madeof a sixth nitride III-V compound semiconductor containing Ga;

a cap layer in contact with the optical guide layer and having asuperlattice structure in which barrier layers are made of the thirdnitride III-V compound semiconductor containing Al and Ga; and

a p-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 17th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an optical guide layer in contact with the activelayer and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the optical guide layer andmade of a third nitride III-V compound semiconductor containing Al andGa; and a p-type clad layer in contact with the cap layer and made of aseventh nitride III-V compound semiconductor containing Al and Ga anddifferent from the third nitride III-V compound semiconductor,comprising:

growing the active layer, the optical guide layer and the cap layer in acarrier gas atmosphere containing substantially no hydrogen andcontaining nitrogen as the major component thereof; and

growing the p-type clad layer in a carrier gas atmosphere containingnitrogen and hydrogen as major components thereof.

According to the 18th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an optical guide layer in contact with the activelayer and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the optical guide layer andmade of a third nitride III-V compound semiconductor containing Al andGa; and a p-type clad layer in contact with the cap layer and made of aseventh nitride III-V compound semiconductor containing Al and Ga anddifferent from the third nitride III-V compound semiconductor,comprising:

growing the active layer, the optical guide layer and the cap layer at agrowth temperature lower than the growth temperature of the p-type cladlayer.

According to the 19th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; an optical guide layer in contact with the intermediatelayer and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the optical guide layer andmade of a third nitride III-V compound semiconductor containing Al andGa; and a p-type clad layer in contact with the cap layer and made of aseventh nitride III-V compound semiconductor containing Al and Ga anddifferent from the third nitride III-V compound semiconductor,comprising:

growing the active layer, the intermediate layer, the optical guidelayer and the cap layer in a carrier gas atmosphere containingsubstantially no hydrogen and containing nitrogen as the major componentthereof; and

growing the p-type clad layer in a carrier gas atmosphere containingnitrogen and hydrogen as major components thereof.

According to the 20th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; an optical guide layer in contact with the intermediatelayer and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the optical guide layer andmade of a third nitride III-V compound semiconductor containing Al andGa; and a p-type clad layer in contact with the cap layer and made of aseventh nitride III-V compound semiconductor containing Al and Ga anddifferent from the third nitride III-V compound semiconductor,comprising:

growing the active layer, the intermediate layer, the optical guidelayer and the cap layer at a growth temperature lower than the growthtemperature of the p-type clad layer.

Typically, the active layer and the intermediate layer are grown under agrowth temperature lower than that of the optical guide layer and thecap layer.

According to the 21st aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; a first optical guide layer in contact with theactive layer and made of an eighth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the first optical guide layerand made of a third nitride III-V compound semiconductor containing Aland Ga; a second optical guide layer in contact with the cap layer andmade of a ninth nitride III-V compound semiconductor containing Ga; anda p-type clad layer in contact with the second optical guide layer andmade of a seventh nitride III-V compound semiconductor containing Al andGa and different from the third nitride III-V compound semiconductor,comprising:

growing the active layer, the first optical guide layer and the caplayer in a carrier gas atmosphere containing substantially no hydrogenand containing nitrogen as the major component thereof; and

growing the second optical guide layer and the p-type clad layer in acarrier gas atmosphere containing nitrogen and hydrogen as majorcomponents thereof.

According to the 22nd aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; a first optical guide layer in contact with theactive layer and made of an eighth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the first optical guide layerand made of a third nitride III-V compound semiconductor containing Aland Ga; a second optical guide layer in contact with the cap layer andmade of a ninth nitride III-V compound semiconductor containing Ga; anda p-type clad layer in contact with the second optical guide layer andmade of a seventh nitride III-V compound semiconductor containing Al andGa and different from the third nitride III-V compound semiconductor,comprising:

growing the active layer, the first optical guide layer and the caplayer at a growth temperature lower than the growth temperature of thesecond optical guide layer and the p-type clad layer.

According to the 23rd aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; a first optical guide layer in contact with theintermediate layer and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the firstoptical guide layer and made of a third nitride III-V compoundsemiconductor containing Al and Ga; a second optical guide layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type clad layer in contact with thesecond optical guide layer and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor, comprising:

growing the active layer, the intermediate layer, the first opticalguide layer and the cap layer in a carrier gas atmosphere containingsubstantially no hydrogen and containing nitrogen as the major componentthereof; and

growing the second optical guide layer and the p-type clad layer in acarrier gas atmosphere containing nitrogen and hydrogen as majorcomponents thereof.

According to the 24th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; a first optical guide layer in contact with theintermediate layer and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the firstoptical guide layer and made of a third nitride III-V compoundsemiconductor containing Al and Ga; a second optical guide layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type clad layer in contact with thesecond optical guide layer and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor, comprising:

growing the active layer, the intermediate layer, the first opticalguide layer and the cap layer at a growth temperature lower than thegrowth temperature of the second optical guide layer and the p-type cladlayer.

Typically, the active layer is grown under a growth temperature lowerthan that of intermediate layer, first optical guide layer and caplayer.

According to the 25th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; a first optical guide layer in contact with theactive layer and made of an eighth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the first optical guide layerand having a superlattice structure in which barrier layers are made ofa third nitride III-V compound semiconductor containing Al and Ga; asecond optical guide layer in contact with the cap layer and made of aninth nitride III-V compound semiconductor containing Ga; and a p-typeclad layer in contact with the second optical guide layer and made of aseventh nitride III-V compound semiconductor containing Al and Ga anddifferent from the third nitride III-V compound semiconductor,comprising:

growing the active layer, the first optical guide layer and the caplayer in a carrier gas atmosphere containing substantially no hydrogenand containing nitrogen as the major component thereof; and

growing the second optical guide layer and the p-type clad layer in acarrier gas atmosphere containing nitrogen and hydrogen as majorcomponents thereof.

According to the 26th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; a first optical guide layer in contact with theactive layer and made of an eighth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the first optical guide layerand having a superlattice structure in which barrier layers are made ofa third nitride III-V compound semiconductor containing Al and Ga; asecond optical guide layer in contact with the cap layer and made of aninth nitride III-V compound semiconductor containing Ga; and a p-typeclad layer in contact with the second optical guide layer and made of aseventh nitride III-V compound semiconductor containing Al and Ga anddifferent from the third nitride III-V compound semiconductor,comprising:

growing the active layer, the first optical guide layer and the caplayer at a growth temperature lower than the growth temperature of thesecond optical guide layer and the p-type clad layer.

According to the 27th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; a first optical guide layer in contact with theintermediate layer and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the firstoptical guide layer and having a superlattice structure in which barrierlayers are made of a third nitride III-V compound semiconductorcontaining Al and Ga; a second optical guide layer in contact with thecap layer and made of a ninth nitride III-V compound semiconductorcontaining Ga; and a p-type clad layer in contact with the secondoptical guide layer and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor, comprising:

growing the active layer, the intermediate layer, the first opticalguide layer and the cap layer in a carrier gas atmosphere containingsubstantially no hydrogen and containing nitrogen as the major componentthereof; and

growing the second optical guide layer and the p-type clad layer in acarrier gas atmosphere containing nitrogen and hydrogen as majorcomponents thereof.

According to the 28th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; a first optical guide layer in contact with theintermediate layer and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the firstoptical guide layer and having a superlattice structure in which barrierlayers are made of a third nitride III-V compound semiconductorcontaining Al and Ga; a second optical guide layer in contact with thecap layer and made of a ninth nitride III-V compound semiconductorcontaining Ga; and a p-type clad layer in contact with the secondoptical guide layer and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor, comprising:

growing the active layer, the intermediate layer, the first opticalguide layer and the cap layer at a growth temperature lower than thegrowth temperature of the second optical guide layer and the p-type cladlayer.

Typically, the active layer and the intermediate layer are grown under agrowth temperature lower than that of the optical guide layer and thecap layer.

According to the 29th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an optical guide layer in contact with the activelayer and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the optical guide layer andhaving a superlattice structure in which barrier layers are made of athird nitride III-V compound semiconductor containing Al and Ga; and ap-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor, comprising:

growing the active layer, the optical guide layer and the cap layer in acarrier gas atmosphere containing substantially no hydrogen andcontaining nitrogen as the major component thereof; and

growing the p-type clad layer in a carrier gas atmosphere containingnitrogen and hydrogen as major components thereof.

According to the 30th aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an optical guide layer in contact with the activelayer and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the optical guide layer andhaving a superlattice structure in which barrier layers are made of athird nitride III-V compound semiconductor containing Al and Ga; and ap-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor, comprising:

growing the active layer, the optical guide layer and the cap layer at agrowth temperature lower than the growth temperature of the p-type cladlayer.

According to the 31st aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; an optical guide layer in contact with the intermediatelayer and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the optical guide layer andhaving a superlattice structure in which barrier layers are made of thethird nitride III-V compound semiconductor containing Al and Ga; and ap-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor, comprising:

growing the active layer, the intermediate layer, the optical guidelayer and the cap layer in a carrier gas atmosphere containingsubstantially no hydrogen and containing nitrogen as the major componentthereof; and

growing the p-type clad layer in a carrier gas atmosphere containingnitrogen and hydrogen as major components thereof.

According to the 32nd aspect of the invention, there is provided amanufacturing method of a semiconductor light emitting device includingan active layer made of a first nitride III-V compound semiconductorcontaining In and Ga; an intermediate layer in contact with the activelayer and made of a second nitride III-V compound semiconductorcontaining In and Ga and different from the first nitride III-V compoundsemiconductor; an optical guide layer in contact with the intermediatelayer and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the optical guide layer andhaving a superlattice structure in which barrier layers are made of thethird nitride III-V compound semiconductor containing Al and Ga; and ap-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor, comprising:

growing the active layer, the intermediate layer, the optical guidelayer and the cap layer at a growth temperature lower than the growthtemperature of the p-type clad layer.

Typically, the active layer and the intermediate layer are grown under agrowth temperature lower than that of the optical guide layer and thecap layer.

According to the 33rd aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

a layer in contact with the layer made of the first nitride III-Vcompound semiconductor, and made of a sixth nitride III-V compoundsemiconductor containing Ga;

a cap layer in contact with the layer made of the sixth nitride III-Vcompound semiconductor, and made of a third nitride III-V compoundsemiconductor containing Al and Ga; and

a p-type layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 34th aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

an intermediate layer in contact with the layer made of the firstnitride III-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor;

a layer in contact with the intermediate layer and made of a sixthnitride III-V compound semiconductor containing Ga;

a cap layer in contact with the layer made of the sixth nitride III-Vcompound semiconductor, and made of a third nitride III-V compoundsemiconductor containing Al and Ga; and

a p-type layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 35th aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

a layer in contact with the layer made of the first nitride III-Vcompound semiconductor, and made of an eighth nitride III-V compoundsemiconductor containing Ga;

a cap layer in contact with the layer made of the eighth nitride III-Vcompound semiconductor, and made of a third nitride III-V compoundsemiconductor containing Al and Ga;

a layer in contact with the cap layer and made of a ninth nitride III-Vcompound semiconductor containing Ga; and

a p-type layer in contact with the layer made of the ninth nitride III-Vcompound semiconductor, and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor.

According to the 36th aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

an intermediate layer in contact with the layer made of the firstnitride III-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor;

a layer in contact with the intermediate layer and made of an eighthnitride III-V compound semiconductor containing Ga;

a cap layer in contact with the layer made of the eighth nitride III-Vcompound semiconductor, and made of a third nitride III-V compoundsemiconductor containing Al and Ga;

a layer in contact with the cap layer and made of a ninth nitride III-Vcompound semiconductor containing Ga; and

a p-type layer in contact with the layer made of the ninth nitride III-Vcompound semiconductor, and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor.

According to the 37th aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

a layer in contact with the layer made of the first nitride III-Vcompound semiconductor, and made of an eighth nitride III-V compoundsemiconductor containing Ga;

a cap layer in contact with the layer made of the eighth nitride III-Vcompound semiconductor, and having a superlattice structure in whichbarrier layers are made of a third nitride III-V compound semiconductorcontaining Al and Ga;

a layer in contact with the cap layer and made of a ninth nitride III-Vcompound semiconductor containing Ga; and

a p-type layer in contact with the layer made of the ninth nitride III-Vcompound semiconductor, and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor.

According to the 38th aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

an intermediate layer in contact with the layer made of the firstnitride III-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor;

a layer in contact with the intermediate layer and made of an eighthnitride III-V compound semiconductor containing Ga;

a cap layer in contact with the layer made of the eighth nitride III-Vcompound semiconductor, and having a superlattice structure in whichbarrier layers are made of a third nitride III-V compound semiconductorcontaining Al and Ga;

a layer in contact with the cap layer and made of a ninth nitride III-Vcompound semiconductor containing Ga; and

a p-type clad layer in contact with the layer made of the ninth nitrideIII-V compound semiconductor, and made of a seventh nitride III-Vcompound semiconductor containing Al and Ga and different from the thirdnitride III-V compound semiconductor.

According to the 39th aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

a layer in contact with the layer made of the first nitride III-Vcompound semiconductor, and made of a sixth nitride III-V compoundsemiconductor containing Ga;

a cap layer in contact with the layer made of the sixth nitride III-Vcompound semiconductor, and having a superlattice structure in whichbarrier layers are made of a third nitride III-V compound semiconductorcontaining Al and Ga; and

a p-type layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 40th aspect of the invention, there is provided asemiconductor device comprising:

a layer made of a first nitride III-V compound semiconductor containingIn and Ga;

an intermediate layer in contact with the layer made of the firstnitride III-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor;

a layer in contact with the intermediate layer and made of a sixthnitride III-V compound semiconductor containing Ga;

a cap layer in contact with the layer made of the sixth nitride III-Vcompound semiconductor, and having a superlattice structure in whichbarrier layers are made of the third nitride III-V compoundsemiconductor containing Al and Ga; and

a p-type clad layer in contact with the cap layer and made of a seventhnitride III-V compound semiconductor containing Al and Ga and differentfrom the third nitride III-V compound semiconductor.

According to the 41st aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; alayer in contact with the layer made of the first nitride III-V compoundsemiconductor, and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the layer made of the sixthnitride III-V compound semiconductor, and made of a third nitride III-Vcompound semiconductor containing Al and Ga; and a p-type layer incontact with the cap layer and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor, comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the layer made of the sixth nitride III-V compoundsemiconductor and the cap layer in a carrier gas atmosphere containingsubstantially no hydrogen and containing nitrogen as the major componentthereof; and

growing the p-type layer in a carrier gas atmosphere containing nitrogenand hydrogen as major components thereof.

According to the 42nd aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; alayer in contact with the layer made of the first nitride III-V compoundsemiconductor, and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the layer made of the sixthnitride III-V compound semiconductor, and made of a third nitride III-Vcompound semiconductor containing Al and Ga; and a p-type layer incontact with the cap layer and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor, comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the layer made of the sixth nitride III-V compoundsemiconductor and the cap layer at a growth temperature lower than thegrowth temperature of the p-type layer.

According to the 43rd aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; a layer in contact with theintermediate layer and made of a sixth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the sixth nitride III-V compound semiconductor, and made of a thirdnitride III-V compound semiconductor containing Al and Ga; and a p-typelayer in contact with the cap layer and made of a seventh nitride III-Vcompound semiconductor containing Al and Ga and different from the thirdnitride III-V compound semiconductor, comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the intermediate layer, the layer made of the sixthnitride III-V compound semiconductor and the cap layer in a carrier gasatmosphere containing substantially no hydrogen and containing nitrogenas the major component thereof; and

growing the p-type layer in a carrier gas atmosphere containing nitrogenand hydrogen as major components thereof.

According to the 44th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; a layer in contact with theintermediate layer and made of a sixth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the sixth nitride III-V compound semiconductor, and made of a thirdnitride III-V compound semiconductor containing Al and Ga; and a p-typelayer in contact with the cap layer and made of a seventh nitride III-Vcompound semiconductor containing Al and Ga and different from the thirdnitride III-V compound semiconductor, comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the intermediate layer, the layer made of the sixthnitride III-V compound semiconductor and the cap layer at a growthtemperature lower than the growth temperature of the p-type clad layer.

Typically, the layer made of the first nitride III-V compoundsemiconductor and the intermediate layer are grown under a growthtemperature lower than that of the layer made of the sixth nitride III-Vcompound semiconductor and the cap layer.

According to the 45th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; alayer in contact with the layer made of the first nitride III-V compoundsemiconductor, and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the eighth nitride III-V compound semiconductor, and made of a thirdnitride III-V compound semiconductor containing Al and Ga; a layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type layer in contact with thelayer made of the ninth nitride III-V compound semiconductor, and madeof a seventh nitride III-V compound semiconductor containing Al and Gaand different from the third nitride III-V compound semiconductor,comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the layer made of the eighth nitride III-V compoundsemiconductor and the cap layer in a carrier gas atmosphere containingsubstantially no hydrogen and containing nitrogen as the major componentthereof; and

growing the layer made of the ninth nitride III-V compound semiconductorand the p-type layer in a carrier gas atmosphere containing nitrogen andhydrogen as major components thereof.

According to the 46th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; alayer in contact with the layer made of the first nitride III-V compoundsemiconductor, and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the eighth nitride III-V compound semiconductor, and made of a thirdnitride III-V compound semiconductor containing Al and Ga; a layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type layer in contact with thelayer made of the ninth nitride III-V compound semiconductor, and madeof a seventh nitride III-V compound semiconductor containing Al and Gaand different from the third nitride III-V compound semiconductor,comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the layer made of the eighth nitride III-V compoundsemiconductor and the cap layer at a growth temperature lower than thegrowth temperature of the layer made of the ninth nitride III-V compoundsemiconductor and the p-type layer.

According to the 47th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; a layer in contact with theintermediate layer and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the eighth nitride III-V compound semiconductor, and made of a thirdnitride III-V compound semiconductor containing Al and Ga; a layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type layer in contact with thelayer made of the ninth nitride III-V compound semiconductor, and madeof a seventh nitride III-V compound semiconductor containing Al and Gaand different from the third nitride III-V compound semiconductor,comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the intermediate layer, the layer made of the eighthnitride III-V compound semiconductor and the cap layer in a carrier gasatmosphere containing substantially no hydrogen and containing nitrogenas the major component thereof; and

growing the layer made of the ninth nitride III-V compound semiconductorand the p-type layer in a carrier gas atmosphere containing nitrogen andhydrogen as major components thereof.

According to the 48th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; a layer in contact with theintermediate layer and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the eighth nitride III-V compound semiconductor, and made of a thirdnitride III-V compound semiconductor containing Al and Ga; a layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type layer in contact with thelayer made of the ninth nitride III-V compound semiconductor, and madeof a seventh nitride III-V compound semiconductor containing Al and Gaand different from the third nitride III-V compound semiconductor,comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the intermediate layer, the layer made of the eighthnitride III-V compound semiconductor and the cap layer at a growthtemperature lower than the growth temperature of the layer made of theninth nitride III-V compound semiconductor and the p-type clad layer.

Typically, the layer made of the first nitride III-V compoundsemiconductor is grown under a growth temperature lower than that of theintermediate layer and the layer made of the eighth nitride III-Vcompound semiconductor.

According to the 49th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; alayer in contact with the layer made of the first nitride III-V compoundsemiconductor, and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the eighth nitride III-V compound semiconductor, and having asuperlattice structure in which barrier layers are made of a thirdnitride III-V compound semiconductor containing Al and Ga; a layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type layer in contact with thelayer made of the ninth nitride III-V compound semiconductor, and madeof a seventh nitride III-V compound semiconductor containing Al and Gaand different from the third nitride III-V compound semiconductor,comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the layer made of the eighth nitride III-V compoundsemiconductor and the cap layer in a carrier gas atmosphere containingsubstantially no hydrogen and containing nitrogen as the major componentthereof; and

growing the layer made of the ninth nitride III-V compound semiconductorand the p-type layer in a carrier gas atmosphere containing nitrogen andhydrogen as major components thereof.

According to the 50th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; alayer in contact with the layer made of the first nitride III-V compoundsemiconductor, and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the eighth nitride III-V compound semiconductor, and having asuperlattice structure in which barrier layers are made of a thirdnitride III-V compound semiconductor containing Al and Ga; a layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type layer in contact with thelayer made of the ninth nitride III-V compound semiconductor, and madeof a seventh nitride III-V compound semiconductor containing Al and Gaand different from the third nitride III-V compound semiconductor,comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the layer made of the eighth nitride III-V compoundsemiconductor and the cap layer at a growth temperature lower than thegrowth temperature of the layer made of the ninth nitride III-V compoundsemiconductor and the p-type clad layer.

According to the 51st aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; a layer in contact with theintermediate layer and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the eighth nitride III-V compound semiconductor, and having asuperlattice structure in which barrier layers are made of a thirdnitride III-V compound semiconductor containing Al and Ga; a layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type layer in contact with thelayer made of a ninth nitride III-V compound semiconductor, and made ofa seventh nitride III-V compound semiconductor containing Al and Ga anddifferent from the third nitride III-V compound semiconductor,comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the intermediate layer, the layer made of the eighthnitride III-V compound semiconductor and the cap layer in a carrier gasatmosphere containing substantially no hydrogen and containing nitrogenas the major component thereof; and

growing the layer made of the ninth nitride III-V compound semiconductorand the p-type layer in a carrier gas atmosphere containing nitrogen andhydrogen as major components thereof.

According to the 52nd aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; a layer in contact with theintermediate layer and made of an eighth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the eighth nitride III-V compound semiconductor, and having asuperlattice structure in which barrier layers are made of a thirdnitride III-V compound semiconductor containing Al and Ga; a layer incontact with the cap layer and made of a ninth nitride III-V compoundsemiconductor containing Ga; and a p-type layer in contact with thelayer made of a ninth nitride III-V compound semiconductor, and made ofa seventh nitride III-V compound semiconductor containing Al and Ga anddifferent from the third nitride III-V compound semiconductor,comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the intermediate layer, the layer made of the eighthnitride III-V compound semiconductor and the cap layer at a growthtemperature lower than the growth temperature of the layer made of theninth nitride III-V compound semiconductor and the p-type clad layer.

Typically, the layer made of the first nitride III-V compoundsemiconductor and the intermediate layer are grown under a growthtemperature lower than that of the layer made of the eighth nitrideIII-V compound semiconductor and the cap layer.

According to the 53rd aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; alayer in contact with the layer made of the first nitride III-V compoundsemiconductor, and made of a sixth nitride II-V compound semiconductorcontaining Ga; a cap layer in contact with the layer made of the sixthnitride III-V compound semiconductor, and having a superlatticestructure in which barrier layers are made of a third nitride III-Vcompound semiconductor containing Al and Ga; and a p-type layer incontact with the cap layer and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor, comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the layer made of the sixth nitride III-V compoundsemiconductor and the cap layer in a carrier gas atmosphere containingsubstantially no hydrogen and containing nitrogen as the major componentthereof; and

growing the p-type layer in a carrier gas atmosphere containing nitrogenand hydrogen as major components thereof.

According to the 54th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; alayer in contact with the layer made of the first nitride III-V compoundsemiconductor, and made of a sixth nitride III-V compound semiconductorcontaining Ga; a cap layer in contact with the layer made of the sixthnitride III-V compound semiconductor, and having a superlatticestructure in which barrier layers are made of a third nitride III-Vcompound semiconductor containing Al and Ga; and a p-type layer incontact with the cap layer and made of a seventh nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor, comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the layer made of the sixth nitride III-V compoundsemiconductor and the cap layer at a growth temperature lower than thegrowth temperature of the p-type layer.

According to the 55th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; a layer in contact with theintermediate layer and made of a sixth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the sixth nitride III-V compound semiconductor, and having asuperlattice structure in which barrier layers are made of the thirdnitride III-V compound semiconductor containing Al and Ga; and a p-typelayer in contact with the cap layer and made of a seventh nitride III-Vcompound semiconductor containing Al and Ga and different from the thirdnitride III-V compound semiconductor, comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the intermediate layer, the layer made of the sixthnitride III-V compound semiconductor and the cap layer in a carrier gasatmosphere containing substantially no hydrogen and containing nitrogenas the major component thereof; and

growing the p-type layer in a carrier gas atmosphere containing nitrogenand hydrogen as major components thereof.

According to the 56th aspect of the invention, there is provided amanufacturing method of a semiconductor device including a layer made ofa first nitride III-V compound semiconductor containing In and Ga; anintermediate layer in contact with the layer made of the first nitrideIII-V compound semiconductor, and made of a second nitride III-Vcompound semiconductor containing In and Ga and different from the firstnitride III-V compound semiconductor; a layer in contact with theintermediate layer and made of a sixth nitride III-V compoundsemiconductor containing Ga; a cap layer in contact with the layer madeof the sixth nitride III-V compound semiconductor, and having asuperlattice structure in which barrier layers are made of the thirdnitride III-V compound semiconductor containing Al and Ga; and a p-typelayer in contact with the cap layer and made of a seventh nitride III-Vcompound semiconductor containing Al and Ga and different from the thirdnitride III-V compound semiconductor, comprising:

growing the layer made of the first nitride III-V compoundsemiconductor, the intermediate layer, the layer made of the sixthnitride III-V compound semiconductor and the cap layer at a growthtemperature lower than the growth temperature of the p-type layer.

Typically, the layer made of the first nitride III-V compoundsemiconductor and the intermediate layer are grown under a growthtemperature lower than that of the layer made of the sixth nitride III-Vcompound semiconductor and the cap layer.

In the 9th to 56th aspects of the invention, the sixth nitride III-Vcompound semiconductor containing Ga, eighth nitride III-V compoundsemiconductor and ninth nitride III-V compound semiconductor layer maycontain In, Al or B, for example, as a group III element other than Ga,and may contain As or P as a group V element. The seventh nitride III-Vcompound semiconductor containing Al and Ga may contain In, or B, forexample, as a group III element other than Al and Ga, and may contain Asor P as a group V element.

In the 9th to 56th aspects of the invention, the band gap of the caplayer is typically larger than the band gap of the p-type clad layer orthe p-type layer. Thickness of the cap layer is preferably equal to ormore than 2 nm to ensure a sufficient effect by the use of the caplayer. However, if the cap layer is excessively thick, the crystallinequality deteriorates in some kinds of composition. To prevent it,thickness of the cap layer is preferably limited not to exceed 20 nm. Ifthe optical guide layer, first optical guide layer, layer made of thesixth nitride III-V compound semiconductor or layer made of the eighthnitride III-V compound is doped with Mg or other p-type impuritysemiconductor, the specific resistance rather increases. Therefore, itis preferably undoped. The optical guide layer, first optical guidelayer, layer made of the sixth nitride III-V compound semiconductor orlayer made of the eighth nitride III-V compound exhibits an n-typeconductivity when it is undoped. Thickness of the optical guide layer,first optical guide layer, layer made of the sixth nitride III-Vcompound semiconductor or layer made of the eighth nitride III-Vcompound is, in general, equal to larger than 8 nm, and it is typicallycontrolled in the range from 10 nm to 100 nm.

As to carrier gas atmosphere used for growth of layers of semiconductorlight emitting devices or semiconductor devices, in order to obtain alayer with a lower resistance, a N₂ gas atmosphere is most preferablyused as the carrier gas atmosphere containing substantially no hydrogenand containing nitrogen as its major component, and a mixed gasatmosphere containing N₂ and H₂ is used as the carrier gas atmospherecontaining nitrogen and hydrogen as its major components.

In the 9th to 56th aspects of the invention, the statement made withreference to the first to eighth aspects of the invention are here againrecommended as far as they are consistent to their natures.

According to the invention summarized above, since the intermediatelayer made of the second nitride III-V compound semiconductor containingIn and Ga and different from the first nitride III-V compoundsemiconductor is provided in contact with the active layer or the layermade of the first nitride III-V compound semiconductor, the intermediatelayer largely alleviates the stress produced in the active layer or thelayer made of the first nitride III-V compound semiconductor, oreffectively prevents Mg used as the p-type dopant from diffusion intothe active layer or the layer made of the first nitride III-V compoundsemiconductor.

Additionally, by optimizing the position of the cap layer, the opticalguide layer or the first optical guide layer can be grown in a goodcrystalline quality as compared with a structure locating the cap layeradjacent to the active layer via the intermediate layer, for example, orthe optical guide layer or the first optical guide layer can beoptimized in thickness.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing a GaN compound semiconductorlaser according to the first embodiment of the invention;

FIG. 2 is a schematic diagram showing an energy band structure of theGaN compound semiconductor laser according to the first embodiment ofthe invention;

FIG. 3 is a schematic diagram showing an energy band structure of a GaNcompound semiconductor laser according to the second embodiment of theinvention;

FIG. 4 is a schematic diagram showing an energy band structure of theGaN compound semiconductor laser according to the third embodiment ofthe invention;

FIG. 5 is a schematic diagram showing an energy band structure of theGaN compound semiconductor laser according to the first embodiment ofthe invention;

FIG. 6 is a cross-sectional view showing a GaN compound semiconductorlaser according to the fifth embodiment of the invention;

FIG. 7 is a schematic diagram showing an energy band structure of theGaN compound semiconductor laser according to the fifth embodiment ofthe invention;

FIG. 8 is a schematic diagram showing measured changes in verticalradiation angle of the GaN compound semiconductor laser according to thefifth embodiment of the invention in response to changes in thickness ofan undoped GaN optical guide layer therein;

FIG. 9 is a cross-sectional view showing a GaN compound semiconductorlaser according to the sixth embodiment of the invention;

FIG. 10 is a schematic diagram showing an energy band structure of theGaN compound semiconductor laser according to the sixth embodiment ofthe invention;

FIG. 11 is a schematic diagram showing an energy band structure of a GaNcompound semiconductor laser according to the seventh embodiment of theinvention;

FIG. 12 is a schematic diagram showing an energy band structure of a GaNcompound semiconductor laser according to the eighth embodiment of theinvention;

FIG. 13 is a schematic diagram showing an energy band structure of a GaNcompound semiconductor laser according to the ninth embodiment of theinvention;

FIG. 14 is a schematic diagram showing an energy band structure of a GaNcompound semiconductor laser according to the tenth embodiment of theinvention;

FIG. 15 is a schematic diagram showing an energy band structure of a GaNcompound semiconductor laser according to the eleventh embodiment of theinvention; and

FIG. 16 is a schematic diagram showing an energy band structure of a GaNcompound semiconductor laser according to the twelfth embodiment of theinvention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Embodiments of the invention will now be explained below with referenceto the drawings.

In all figures showing embodiments of the invention, identical orequivalent components are labeled with common reference numerals.

FIG. 1 shows a GaN compound semiconductor laser according to the firstembodiment of the invention. This GaN compound semiconductor laser has aridge structure and a SCH (separate confinement heterostructure)structure.

As shown in FIG. 1, the GaN compound semiconductor laser according tothe first embodiment includes an undoped GaN layer 3 grown by lateralcrystal growth technique such as ELO: n-type GaN contact layer 4; n-typeAlGaN clad layer 5; n-type GaN optical guide layer 6; active layer 7having an undoped In_(x)Ga_(1-x)N/In_(y)Ga_(1-y)N multiquantum wellstructure, for example; n-type undoped InGaN deterioration preventinglayer 8; p-type AlGaN cap layer 9; p-type GaN optical guide layer 10;p-type AlGaN clad layer 11; and p-type GaN contact layer 12 that aresequentially overlaid on a c-plane sapphire substrate 1 via an undopedGaN buffer layer 2 grown at a low temperature.

The undoped GaN buffer layer 2 is 30 nm thick, for example. The undopedGaN layer 3 is 0.5 μm thick, for example. The n-type GaN contact layer 4is 4 μm thick, for example, and silicon (Si), for example, is doped asan n-type impurity. The n-type AlGaN clad layer 5 is 1.0 μm thick, forexample, and Si, for example, is doped as an n-type impurity. Its Alcomposition may be 0.07, for example. The n-type GaN optical guide layer6 is 0.1 μm thick, for example, and Si, for example, is doped as ann-type impurity. In the active layer 7 of the undopedIn_(x)Ga_(1-x)N/In_(y)Ga_(1-y)N multiquantum well structure, eachIn_(x)Ga_(1-x)N layer as a well layer may be 3.5 nm thick, and x=0.14.Each In_(y)Ga_(1-y)N layer as a barrier layer may be 7 nm thick, andy=0.02. The active layer 7 includes three such well layers.

The undoped InGaN deterioration preventing layer 8 has a gradedstructure in which the indium composition gradually, monotonouslydecreases from the surface in contact with the active layer toward thesurface in contact with the p-type AlGaN cap layer 9. The indiumcomposition along the surface in contact with the active layer 7 isequal to the Indium composition y of the In_(y)Ga_(1-y)N barrier layersof the active layer 7, and the indium composition along the surface incontact with the p-type AlGaN cap layer is 0. The undoped InGaNdeterioration preventing layer 8 is 20 nm thick, for example.

The p-type AlGaN cap layer 9 is 10 nm thick, for example, and magnesium(Mg), for example, is doped as a p-type impurity. Al composition of thep-type AlGaN cap layer 9 may be 0.2, for example. As already explained,the p-type AlGaN cap layer 9 is provided to prevent the active layer 7from deterioration by elimination of In therefrom during growth of thep-type GaN optical guide layer 10, p-type AlGaN clad layer 11 and p-typeGaN contact layer 12 and simultaneously prevent overflow of carriers(electrons) from the active layer 9. Thickness of the p-type GaN opticalguide layer 10 is 0.1 μm, for example, and Mg, for example, is doped asa p-type impurity. Thickness of the p-type AlGaN clad layer 11 is 0.5μm, for example, and Mg, for example, is doped as a p-type impurity. ItsAl composition is 0.07, for example. Thickness of the p-type GaN contactlayer 12 is 0.1 μm, for example, and Mg, for example, is doped as ap-type impurity.

An upper part of the n-type GaN contact layer 4, n-type AlGaN clad layer5, n-type GaN optical guide layer 6, active layer 7, undoped InGaNdeterioration preventing layer 8, p-type AlGaN cap layer 9, p-type GaNoptical guide layer 10 and p-type GaN clad layer 11 are shaped into amesa configuration of a predetermined width. In the upper part of thep-type AlGaN clad layer 11 and the p-type contact layer 13 in the mesaportion, a ridge 13 is formed to extend in the <11-20> direction, forexample. Width of the ridge 13 is 3 μm, for example.

An insulating film 14 such as a SiO₂ film having the thickness of 0.3μm, for example, is formed to cover the entirety of the mesa portion.The insulating film 14 is provided for the purpose of electricalinsulation and surface protection. The insulating film 14 has anaperture above the ridge 13, and a p-side electrode 15 is in contactwith the p-type GaN contact layer 13 through the aperture 14 a. Thep-side electrode 15 has a multi-layered structure including sequentiallyoverlaid Pd film, Pt film and Au film, which are 10 nm, thick, 100 nmthick and 300 nm thick, for example, respectively. The insulating film14 has another aperture 14 b in a predetermined portion adjacent themesa portion, and an n-side electrode 16 is in contact with the n-typeGaN contact layer 4 through the aperture 14 b. The n-side electrode hasa multi-layered structure including sequentially overlaid Ti film, Ptyfilm and Au film, which are 10 nm thick, 50 nm thick and 100 nm thick,for example, respectively.

FIG. 2 shows an energy band structure (conduction band) of a substantialpart of the GaN compound semiconductor laser. In FIG. 2, E_(c) denotesthe bottom energy of the conduction band.

Next explained is a manufacturing method of the GaN compoundsemiconductor laser according to the first embodiment.

First prepared is a c-plane sapphire substrate 1 with a surface cleanedby thermal cleaning, for example, and the undoped GaN buffer layer 2 isgrown on the c-plane sapphire substrate 1 by metal organic chemicalvapor deposition (MOCVD) at a temperature around 500° C., for example.Thereafter, the undoped GaN layer 3 is grown by MOCVD at the growthtemperature of 1000° C., for example, by lateral crystal growthtechnique such as ELO.

Consecutively, the n-type GaN contact layer 4, n-type AlGaN clad layer5, n-type GaN optical guide layer 6, active layer 7 of the undopedIn_(x)Ga_(1-x)N/In_(y)Ga_(1-y)N multiquantum well structure, undopedInGaN deterioration preventing layer 8, p-type AlGaN cap layer 9, p-typeGaN optical guide layer 10, p-type AlGaN clad layer 11 and p-type GaNcontact layer 12 are sequentially grown on the undoped GaN layer 3 byMOCVD. For growth of the layers not containing In, namely, the n-typeGaN contact layer 4, n-type AlGaN clad layer 5, n-type GaN optical guidelayer 6, p-type AlGaN cap layer 9, p-type GaN optical guide layer 10,p-type AlGaN clad layer 11 and p-type GaN contact layer 12, the growthtemperature adjusted to 1000° C., for example. For growth of the activelayer 7 having the Ga_(1-x)In_(x)N/Ga_(1-y)In_(y)N multiquantum wellstructure, which does not contain In, the growth temperature iscontrolled within 700 to 800° C. for example, e.g. at 730° C. forexample. For growth of the undoped InGaN deterioration-preventing layer8, its growth temperature is set at the same value as the growthtemperature of the active layer 7, namely, 730° C., for example, at thebeginning of the growth, and thereafter, it is gradually raisedlinearly, for example, such that it rises up to the same growthtemperature as that of the p-type AlGaN cap layer 9, namely 835° C. forexample, at the end of the growth.

As to source materials of these GaN compound semiconductor layers,trimethyl gallium ((CH₃)₃Ga, TMG) is used as the source material of Ga,trimethyl aluminum ((CH₃)₃Al, TMA) is used as the source material of Al,trimethyl indium ((CH₃)₃In, TMI) is used as the source material of In,and NH₃ is used as the source material of N, for example. Carrier gasmay be H₂, for example. As to dopants, silane (SiH₄), for example, isused as the n-type dopant, and bis=methylcyclopentadienile magnesium((CH₃C₅H₄)₂Mg) or bis=cyclopentadienile magnesium ((C₅H₅)₂Mg), forexample, is used as the p-type dopant.

In the next process, the c-plane sapphire substrate 1 having the GaNcompound semiconductor layers grown thereon is taken out of the MOCVDapparatus. Then a SiO₂ film (not shown), 0.1 μm thick, for example isformed on the entire surface of the p-type GaN contact layer 12 by CVD,vacuum evaporation, sputtering, or the like, for example. After that, onthis SiO₂ film, a resist pattern (not shown) of a predetermined geometrycorresponding to the shape of the mesa portion is formed byphotolithography. Using this resist pattern as a mask, the SiO₂ film isnext etched and patterned by wet etching using an etching liquid of thefluoric acid series, or by RIE using an etching gas containing fluorine,such as CF₄ or CHF₃. Subsequently, using the SiO₂ film of thepredetermined geometry as a mask, etching is carried out by RIE, forexample, to the depth reaching the n-type GaN contact layer 4. As theetching gas for RIE, a chlorine-series gas may be used as the etchinggas, for example. As a result of this etching, upper part of the n-typeGaN contact layer 4, n-type AlGaN cladding layer 5, n-type GaN waveguidelayer 6, active layer 7, undoped InGaN deterioration-preventing layer 8,p-type AlGaN cap layer 9, p-type GaN waveguide layer 10, p-type AlGaNcladding layer 11 and p-type GaN contact layer 12 are patterned into amesa configuration.

After that, the SiO₂ film used as the etching mask is removed, andanother SiO₂ film (not shown), 0.2 μm thick for example, is again formedon the entire substrate surface by CVD, vacuum evaporation orsputtering, for example. Thereafter, a resist pattern (not shown) of apredetermined geometry corresponding to the shape of the ridge portionis formed on the SiO₂ film by photolithography. After that, using thisresist pattern as a mask, the SiO₂ film is selectively etched into apattern corresponding to the ridge portion by wet etching using anetching liquid of the fluoric acid series, or by RIE using an etchinggas containing fluorine, such as CF₄ or CHF₃.

In the next process, using the SiO₂ film as a mask, the p-type AlGaNcladding layer 11 is selectively etched by RIE to a predetermined depthto make out the ridge 13. In this RIE process, a chlorine-series gas maybe used as the etching gas, for example.

After that, the SiO₂ film used as the etching mask is removed, and theinsulating layer 14 such as a SiO₂ film, 0.3 μm thick for example, isformed on the entire substrate surface by CVD, vacuum evaporation orsputtering, for example.

Subsequently, a resist pattern (not shown) is formed to cover aselective part of the insulating film 14 excluding the region for then-side electrode by photolithography.

Next using this resist pattern as a mask, the insulating film 14 isselectively etched to form the aperture 14 b.

In the next process, maintaining the resist pattern there, a Ti film, Ptfilm and Au film are sequentially deposited on the entire substratesurface by vacuum evaporation, for example. Thereafter, the resistpattern is removed together with the overlying part of the Ti film, Ptfilm and Au film (lift-off). As a result, the n-side electrode 16 isformed in contact with the n-type GaN contact layer 4 through theaperture 14 b in the insulating film 14. The Ti film, Pt film and Aufilm forming the n-side electrode 16 are, respectively, 10 nm thick, 50nm thick and 100 nm thick. An alloying process is next carried out formaking ohmic contact of the n-side electrode 16.

Subsequently, after the aperture 14 a is formed by selectively removingthe insulating film 14 from above the ridge 13 by etching in a similarprocess, and the p-side electrode 15 having the Pd/Pt/Au structure incontact with the p-type GaN contact layer 12 through the aperture 14 ais formed in the same manner as the n-side electrode 16. Thereafter, analloying process is carried out for making ohmic contact of the p-sideelectrode 15.

After that, the substrate having the laser structure thereon is dividedinto bars by cleavage, for example, to make out opposite cavity edges,and after the cavity edges are processed by edge coating, each bar isdivided into chips by cleavage, or the like.

Through those steps, the intended GaN compound semiconductor laserhaving the ridge structure and the SCH structure is completed.

GaN compound semiconductor lasers according to the first embodiment andGaN semiconductor lasers not including the undoped InGaN deteriorationpreventing layer but equal to the former lasers in the other respectswere prepared and subjected to a life test. As a result, GaN compoundsemiconductor lasers according to the first embodiment exhibited verysmall initial deterioration rates as compared with the latter GaNsemiconductor lasers, and although the operation currents of the formerlasers tended to gradually increase with time, their gradients were verysmall and negligible levels. This life test was carried out under thecondition of optical output being 30 mW and atmosphere temperature being60° C. for both the former and latter lasers. Additionally,electroluminescent emission of these GaN compound semiconductor laserswas observed. As a result, although noticeably uneven emission wasobserved in the latter GaN compound semiconductors, no uneven emissionwas observed in the GaN compound semiconductor lasers according to thefirst embodiment.

As explained above, according to the first embodiment, since the laserincludes the undoped InGaN deterioration preventing layer 8 in contactwith the active layer 7 and the p-type AlGaN cap layer 9 in contact withthe undoped InGaN deterioration preventing layer, the undoped InGaNdeterioration preventing layer 8 largely alleviates the stress producedin the active layer 7 by the p-type AlGaN cap layer 9, and effectivelyprevents Mg used as p-type dopants of p-type layers from diffusing intothe active layer 7. As a result, the high-performance GaN compoundsemiconductor laser elongated in lifetime, highly reliable and free fromemission unevenness can be realized.

Next explained is a GaN compound semiconductor laser according to thesecond embodiment of the invention. FIG. 3 is an energy band diagram ofthis GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the secondembodiment, Indium composition in the undoped InGaN deteriorationpreventing layer is uniform throughout the entire thickness thereof, andthe indium composition is adjusted to a value smaller than the Indiumcomposition y of the barrier layers in the active layer 7, namely 0.02,for example. In the other respects, its structure is identical to thatof the GaN compound semiconductor laser according to the firstembodiment. So, its explanation is omitted here.

This GaN compound semiconductor laser can be manufactured by the samemethod as that of the GaN compound semiconductor laser according to thefirst embodiment except that the undoped InGaN deterioration preventinglayer 8 is grown under a constant growth temperature.

The second embodiment also ensures the same advantages as those of thefirst embodiment.

Next explained is a GaN compound semiconductor laser according to thethird embodiment of the invention. FIG. 4 is an energy band diagram ofthis GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the thirdembodiment, Indium composition of the undoped InGaN deteriorationpreventing layer is uniform throughout the entire thickness thereof, andthe indium composition is adjusted to the same value as the Indiumcomposition y of the barrier layers in the active layer 7. Thickness ofthe undoped InGaN deterioration preventing layer 8 is adjusted such thatthe sum of its own thickness and the thickness of one of the barrierlayers of the active layer 7 nearest thereto is at least 15 nm,preferably not thinner than 17 nm, more preferably not thinner than 20nm, or still more preferably not thinner than 25 nm. In the otherrespects, its structure is identical to that of the GaN compoundsemiconductor laser according to the first embodiment. So, itsexplanation is omitted here.

Here again, this GaN compound semiconductor laser can be manufactured bythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment except that the undoped InGaNdeterioration preventing layer 8 is grown under a constant growthtemperature.

The third embodiment also ensures the same advantages as those of thefirst embodiment.

Next explained is a GaN compound semiconductor laser according to thefourth embodiment of the invention. FIG. 5 is an energy band diagram ofthis GaN compound semiconductor laser.

The GaN compound semiconductor laser according to the fourth embodimentis so configured that the undoped InGaN deterioration preventing layer 8is in contact with the active layer 7, the p-type GaN optical guidelayer 10 is in contact with the undoped InGaN deterioration preventinglayer 8, and the p-type AlGaN cap layer 9 is in contact with the p-typeGaN optical guide layer 10. Distribution of the indium composition inthe undoped InGaN deterioration preventing layer 8 is identical to thatof the first embodiment. In the other respects, its structure isidentical to that of the GaN compound semiconductor laser according tothe first embodiment. So, its explanation is omitted here.

Here again, this GaN compound semiconductor laser can be manufactured bythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment.

The fourth embodiment also ensures the same advantages as those of thefirst embodiment.

Next explained is a GaN compound semiconductor laser according to thefifth embodiment of the invention. FIG. 6 shows the GaN compoundsemiconductor laser according to the fifth embodiment. FIG. 7 is anenergy band diagram of this GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the fifthembodiment, an undoped GaN optical guide layer 17 is formed in contactwith the active layer; the p-type AlGaN cap layer 9 is in contact withthe undoped GaN optical guide layer 17; and a p-type AlGaN/GaNsuperlattice clad layer 18 is formed in contact with the p-type AlGaNcap layer 9. The laser of this embodiment does not include the undopedInGaN deterioration preventing layer 8. The undoped GaN optical guidelayer 17 exhibits n-type conductivity. Thickness of the undoped GaNoptical guide layer 17 is usually 10-100 nm; however, it is limited to20˜40 nm in this embodiment. The p-type AlGaN/GaN superlattice cladlayer 18 has a structure alternately stacking undoped□AlGaN layers asbarrier layers each having the thickness of 2.5 nm and Al composition of12%, for example, and Mg-doped GaN layers as well layers each having thethickness of 2.5 nm here again, for example, and the total thickness ofthe clad layer 18 is, for example, 0.5 μm. For the purpose of preventingelectrons injected into the active layer from moving through the p-typeAlGaN cap layer 9 to the p-type AlGaN/GaN superlattice clad layer 18 bytunneling, distance between the p-type AlGaN cap layer 9 and nearest oneof the barrier layers of the p-type AlGaN/GaN superlattice clad layer 18is adjusted to a value capable of preventing the tunneling, namely about10 nm, for example. The purpose of using the p-type AlGaN/GaNsuperlattice clad layer 18 is to facilitate holes to move therethroughby tunneling. In the other respects, the structure of the laser shownhere is identical to that of the GaN compound semiconductor laseraccording to the first embodiment. So, its explanation is omitted here.

This GaN compound semiconductor laser can be manufactured by essentiallythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment. In this embodiment, however, thefollowing special conditions are used for growth temperature and carriergas when growing individual layers. For example, growth temperature isset at 1000° C. for growth of layers from the undoped GaN layer 3 to then-type AlGaN clad layer 5, at 800° C. for growth of layers from then-type GaN optical guide layer 6 to the p-type AlGaN cap layer 9, and at1000° C. for growth of the p-type AlGaN/GaN superlattice clad layer 18and the p-type GaN contact layer 12. As to carrier gas, a mixed gasatmosphere containing N₂ and H₂ is used for growth of layers from theundoped GaN layer 3 to the n-type AlGaN clad layer 5, a N₂ atmosphere isused for growth of layers from the n-type GaN optical guide layer 6 tothe p-type AlGaN cap layer 9, and a mixed gas atmosphere containing N₂and H₂ is used for growth of the p-type AlGaN/GaN superlattice cladlayer 18 and the p-type GaN contact layer 12. In this case, since thecarrier gas atmosphere used for the growth up to the p-type AlGaN caplayer 9 after the growth of the active layer 7 is the N₂ atmosphere anddoes not contain H₂, elimination of In from the active layer 7 isprevented, and the active layer 7 is prevented from deterioration.Additionally, the carrier gas atmosphere used for the growth of thep-type AlGaN/GaN superlattice clad layer 18 and the p-type GaN contactlayer 12 is the mixed gas atmosphere containing N₂ and H₂, these p-typelayers can be grown in a good crystalline quality.

FIG. 8 shows a result of measurement to know how the vertical beamdivergent angle of the semiconductor laser, i.e. its vertical radiationangle (θ⊥), changes with thickness of the undoped GaN optical guidelayer 17. It is appreciated from FIG. 8 that the vertical radiationangle can be limited within 19˜22 degrees by limiting the thickness ofthe undoped GaN optical guide layer 17 within 20˜40 nm. As compared tovertical radiation angles of conventional GaN semiconductor lasers aslarge as 27˜30 degrees, the vertical radiation angle of thesemiconductor laser according to this embodiment is much less.

According to the fifth embodiment, since the semiconductor laser is soconfigured that the active layer 7, undoped GaN optical guide layer 17,p-type AlGaN cap layer 9 and p-type AlGaN/GaN superlattice clad layer 18sequentially lie in contact and the undoped GaN optical guide layer 17is as thin as 20˜40 nm, it is possible to significantly reduce thevertical radiation angle of the GaN compound semiconductor laser andthereby reduce the aspect ratio of the radiation angle (θ⊥/θ□ where θ□is the horizontal radiation angle). Moreover, since the p-type AlGaN caplayer 9 is in contact with the p-type AlGaN/GaN superlattice clad layer18, symmetry of the intensity distribution of light in far-field imagescan be improved. This type of GaN compound semiconductor laser isespecially suitable for use as the light source of an optical discdevice.

Additionally, since the undoped GaN optical guide layer 17 is grown indirect contact with the active layer 7, its crystalline quality isimproved, and the lifetime of the GaN compound semiconductor laser iselongated accordingly.

Furthermore, since the undoped GaN optical guide layer 17 is as thin as20˜40 nm, and its specific resistance is smaller than that of a p-typeGaN optical guide layer doped with Mg as its p-type impurity, serialresistance of the GaN compound semiconductor laser can be reduced, andits drive voltage can be reduced accordingly.

Next explained is a GaN compound semiconductor laser according to thesixth embodiment of the invention. FIG. 9 shows the GaN compoundsemiconductor laser according to the sixth embodiment. FIG. 10 is anenergy band diagram of this GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the sixthembodiment, the undoped InGaN deterioration preventing layer 8 is incontact with the active layer 7; the undoped GaN optical guide layer 17is in contact with the undoped InGaN deterioration preventing layer 8;the p-type AlGaN cap layer 9 is in contact with the undoped GaN opticalguide layer 17; and the p-type AlGaN/GaN superlattice clad layer 18 isin contact with the p-type AlGaN cap layer 9. Indium composition in theundoped InGaN deterioration preventing layer 8 is equal to that of thesecond embodiment. In the other respects, the structure of the lasershown here is identical to those of the GaN compound semiconductorlasers according to the first and fifth embodiments. So, its explanationis omitted here.

This GaN compound semiconductor laser can be manufactured by essentiallythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment. In this embodiment, however, thefollowing special conditions are used for growth temperature and carriergas when growing individual layers. For example, growth temperature isset at 1000° C. for growth of layers from the undoped GaN layer 3 to then-type AlGaN clad layer 5, at 800° C. for growth of layers from then-type GaN optical guide layer 6 to the p-type undoped InGaNdeterioration preventing layer 8, at 850° C. for growth of the undopedGaN optical guide layer 17 and the p-type AlGaN cap layer 9, and at1000° C. for growth of the p-type AlGaN/GaN superlattice clad layer 18and the p-type GaN contact layer 12. As to carrier gas, a mixed gasatmosphere containing N₂ and H₂ is used for growth of layers from theundoped GaN layer 3 to the n-type AlGaN clad layer 5, a N₂ atmosphere isused for growth of layers from the n-type GaN optical guide layer 6 tothe p-type AlGaN cap layer 9, and a mixed gas atmosphere containing N₂and H₂ is used for growth of the p-type AlGaN/GaN superlattice cladlayer 18 and the p-type GaN contact layer 12. In this case, since thecarrier gas atmosphere used for the growth up to the p-type AlGaN caplayer 9 after the growth of the active layer 7 is the N₂ atmosphere anddoes not contain H₂, elimination of In from the active layer 7 isprevented, and the active layer 7 is prevented from deterioration.Additionally, the carrier gas atmosphere used for the growth of thep-type AlGaN/GaN superlattice clad layer 18 and the p-type GaN contactlayer 12 is the mixed gas atmosphere containing N₂ and H₂, these p-typelayers can be grown in a good crystalline quality. 10 According to thesixth embodiment, since the semiconductor laser is so configured thatthe active layer 7, undoped InGaN deterioration preventing layer 8,undoped GaN optical guide layer 17, p-type AlGaN cap layer 9 and p-typeAlGaN/GaN superlattice clad layer 18 sequentially lie in contact and theundoped GaN optical guide layer 17 is as thin as 20˜40 nm, the sameadvantages as those of the fifth embodiment can be obtained, andsimultaneously, since the undoped InGaN deterioration preventing layer 8is provided adjacent to the active layer 7, the same advantages as thoseof the first embodiment can be obtained as well.

Next explained is a GaN compound semiconductor laser according to theseventh embodiment of the invention. FIG. 11 is an energy band diagramof this GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the seventhembodiment, the undoped GaN optical guide layer 17 is provided incontact with the active layer 7; the p-type AlGaN cap layer 9 is incontact with the undoped GaN optical guide layer 17; the p-type GaNoptical guide layer 10 is in contact with the p-type AlGaN cap layer 9;and the p-type AlGaN/GaN superlattice clad layer 18 is in contact withthe p-type GaN optical guide layer 10. In the other respects, thestructure of the laser shown here is identical to those of the GaNcompound semiconductor lasers according to the first and fifthembodiments. So, its explanation is omitted here.

This GaN compound semiconductor laser can be manufactured by essentiallythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment. In this embodiment, however, thefollowing special conditions are used for growth temperature and carriergas when growing individual layers. For example, growth temperature isset at 1000° C. for growth of layers from the undoped GaN layer 3 to then-type AlGaN clad layer 5, at 800° C. for growth of layers from then-type GaN optical guide layer 6 to the p-type AlGaN cap layer 9, and at1000° C. for growth of layers from the p-type GaN optical guide layer 10to the p-type GaN contact layer 12. As to carrier gas, a mixed gasatmosphere containing N₂ and H₂ is used for growth of layers from theundoped GaN layer 3 to the n-type AlGaN clad layer 5, a N₂ atmosphere isused for growth of layers from the n-type GaN optical guide layer 6 tothe p-type AlGaN cap layer 9, and a mixed gas atmosphere containing N₂and H₂ is used for growth of layers from the p-type GaN optical guidelayer 10 to the p-type GaN contact layer 12. In this case, since thecarrier gas atmosphere used for the growth up to the p-type AlGaN caplayer 9 after the growth of the active layer 7 is the N₂ atmosphere anddoes not contain H₂, elimination of In from the active layer 7 isprevented, and the active layer 7 is prevented from deterioration.Additionally, the carrier gas atmosphere used for the growth of thep-type GaN optical guide layer 10, p-type AlGaN/GaN superlattice cladlayer 18 and p-type GaN contact layer 12 is the mixed gas atmospherecontaining N₂ and H₂, these p-type layers can be grown in a goodcrystalline quality.

According to the seventh embodiment, since the semiconductor laser isconfigured such that the active layer 7, undoped InGaN deteriorationpreventing layer 8, undoped GaN optical guide layer 17, p-type AlGaN caplayer 9 and p-type AlGaN/GaN superlattice clad layer 18 sequentially liein contact and the undoped GaN optical guide layer 17 is as thin as20˜40 nm, the same advantages as those of the fifth embodiment can beobtained.

Next explained is a GaN compound semiconductor laser according to theeighth embodiment of the invention. FIG. 12 is an energy band diagram ofthis GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the eighthembodiment, the undoped InGaN deterioration preventing layer 8 is incontact with the active layer 7; the undoped GaN optical guide layer 17is provided in contact with the undoped InGaN deterioration preventinglayer 8; the p-type AlGaN cap layer 9 is in contact with the undoped GaNoptical guide layer 17; the p-type GaN optical guide layer 10 is incontact with the p-type AlGaN cap layer 9; and the p-type AlGaN/GaNsuperlattice clad layer 18 is in contact with the p-type GaN opticalguide layer 10. Indium composition in the undoped InGaN deteriorationpreventing layer 8 is equal to that of the second embodiment. In theother respects, the structure of the laser shown here is identical tothose of the GaN compound semiconductor lasers according to the firstand fifth embodiments. So, its explanation is omitted here.

This GaN compound semiconductor laser can be manufactured by essentiallythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment. In this embodiment, however, thefollowing special conditions are used for growth temperature and carriergas when growing individual layers. For example, growth temperature isset at 1000° C. for growth of layers from the undoped GaN layer 3 to then-type AlGaN clad layer 5, at 800° C. for growth of the n-type GaNoptical guide layer 6 and the active layer 7, at 860° C. for growth oflayers from the undoped InGaN deterioration preventing layer 8 to thep-type AlGaN cap layer 9, and at 1000° C. for growth of layers from thep-type GaN optical guide layer 10 to the p-type GaN contact layer 12. Asto carrier gas, a mixed gas atmosphere containing N₂ and H₂ is used forgrowth of layers from the undoped GaN layer 3 to the n-type AlGaN cladlayer 5, a N₂ atmosphere is used for growth of layers from the n-typeGaN optical guide layer 6 to the p-type AlGaN cap layer 9, and a mixedgas atmosphere containing N₂ and H₂ is used for growth of layers fromthe p-type GaN optical guide layer 10 to the p-type GaN contact layer12. In this case, since the carrier gas atmosphere used for the growthup to the p-type AlGaN cap layer 9 after the growth of the active layer7 is the N₂ atmosphere and does not contain H₂, elimination of In fromthe active layer 7 is prevented, and the active layer 7 is preventedfrom deterioration. Additionally, the carrier gas atmosphere used forthe growth of the p-type GaN optical guide layer 10, p-type AlGaN/GaNsuperlattice clad layer 18 and p-type GaN contact layer 12 is the mixedgas atmosphere containing N₂ and H₂, these p-type layers can be grown ina good crystalline quality.

According to the eighth embodiment, since the semiconductor laser isconfigured such that the active layer 7, undoped InGaN deteriorationpreventing layer 8, undoped GaN optical guide layer 17, p-type AlGaN caplayer 9, p-type GaN optical guide layer 10 and p-type AlGaN/GaNsuperlattice clad layer 18 sequentially lie in contact and the undopedGaN optical guide layer 17 is as thin as 20˜40 nm, the same advantagesas those of the fifth embodiment can be obtained. Additionally, sincethe undoped InGaN deterioration preventing layer is provided in contactwith the active layer 7, the same advantages as those of the firstembodiment are obtained.

Next explained is a GaN compound semiconductor laser according to theninth embodiment of the invention. FIG. 13 is an energy band diagram ofthis GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the ninthembodiment, the undoped GaN optical guide layer 17 is in contact withthe active layer 7; a p-type AlGaN/GaN superlattice cap layer 19 isformed in contact with the undoped GaN optical guide layer 17; thep-type GaN optical guide layer 10 is in contact with the p-typeAlGaN/GaN superlattice cap layer 19; and the p-type AlGaN/GaNsuperlattice clad layer 18 is in contact with the p-type GaN opticalguide layer 10. The p-type AlGaN/GaN superlattice cap layer 19 has astructure alternately stacking undoped AlGaN layers as barrier layerseach having the thickness of 2.5 nm and Al composition of 12%, forexample, and Mg-doped GaN layers as well layers each having thethickness of 2.5 nm here again, for example, and the total thickness ofthe cap layer 19 is, for example, 100 nm. In the other respects, thestructure of the laser shown here is identical to that of the GaNcompound semiconductor laser according to the first embodiment. So, itsexplanation is omitted here.

This GaN compound semiconductor laser can be manufactured by essentiallythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment. In this embodiment, however, thefollowing special conditions are used for growth temperature and carriergas when growing individual layers. For example, growth temperature isset at 1000° C. for growth of layers from the undoped GaN layer 3 to then-type AlGaN clad layer 5, at 800° C. for growth of layers from then-type GaN optical guide layer 6 to the p-type AlGaN/GaN superlatticecap layer 19, and at 1000° C. for growth of layers from the p-type GaNoptical guide layer 10 to the p-type GaN contact layer 12. As to carriergas, a mixed gas atmosphere containing N₂ and H₂ is used for growth oflayers from the undoped GaN layer 3 to the n-type AlGaN clad layer 5, aN₂ atmosphere is used for growth of layers from the n-type GaN opticalguide layer 6 to the p-type AlGaN cap layer 9, and a mixed gasatmosphere containing N₂ and H₂ is used for growth of layers from thep-type GaN optical guide layer 10 to the p-type GaN contact layer 12. Inthis case, since the carrier gas atmosphere used for the growth up tothe p-type AlGaN/GaN superlattice cap layer 19 after the growth of theactive layer 7 is the N₂ atmosphere and does not contain H₂, eliminationof In from the active layer 7 is prevented, and the active layer 7 isprevented from deterioration. Additionally, the carrier gas atmosphereused for the growth of the p-type GaN optical guide layer 10, p-typeAlGaN/GaN superlattice clad layer 18 and the p-type GaN contact layer 12is the mixed gas atmosphere containing N₂ and H₂, these p-type layerscan be grown in a good crystalline quality.

According to the ninth embodiment, since the semiconductor laser isconfigured such that the active layer 7, undoped GaN optical guide layer17, p-type AlGaN/GaN superlattice cap layer 19, p-type GaN optical guidelayer 10 and p-type AlGaN/GaN superlattice clad layer 18 andsequentially lie in contact and the undoped GaN optical guide layer 17is as thin as 20˜40 nm, the same advantages as those of the fifthembodiment can be obtained.

Next explained is a GaN compound semiconductor laser according to thetenth embodiment of the invention. FIG. 14 is an energy band diagram ofthis GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the tenthembodiment, the undoped InGaN deterioration preventing layer 8 is incontact with the active layer 7; the undoped GaN optical guide layer 17is formed in contact with the undoped InGaN deterioration preventinglayer 8; the p-type AlGaN/GaN superlattice cap layer 19 is formed incontact with the undoped GaN optical guide layer 17; the p-type GaNoptical guide layer 10 is in contact with the p-type AlGaN/GaNsuperlattice cap layer 19; and the p-type AlGaN/GaN superlattice cladlayer 18 is in contact with the p-type GaN optical guide layer 10.Indium composition in the undoped InGaN deterioration preventing layer 8is equal to that of the second embodiment. In the other respects, thestructure of the laser shown here is identical to those of the GaNcompound semiconductor lasers according to the first and fifthembodiments. So, its explanation is omitted here.

This GaN compound semiconductor laser can be manufactured by essentiallythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment. In this embodiment, however, thefollowing special conditions are used for growth temperature and carriergas when growing individual layers. For example, growth temperature isset at 1000° C. for growth of layers from the undoped GaN layer 3 to then-type AlGaN clad layer 5, at 800° C. for growth of layers from then-type GaN optical guide layer 6 to the undoped InGaN deteriorationpreventing layer 8, at 870° C. for growth of the undoped GaN opticalguide layer 17 and the p-type AlGaN/GaN superlattice cap layer 19, andat 1000° C. for growth of layers from the p-type GaN optical guide layer10 to the p-type GaN contact layer 12. As to carrier gas, a mixed gasatmosphere containing N₂ and H₂ is used for growth of layers from theundoped GaN layer 3 to the n-type AlGaN clad layer 5, a N₂ atmosphere isused for growth of layers from the n-type GaN optical guide layer 6 tothe p-type AlGaN/GaN superlattice cap layer 19, and a mixed gasatmosphere containing N₂ and H₂ is used for growth of layers from thep-type GaN optical guide layer 10 to the p-type GaN contact layer 12. Inthis case, since the carrier gas atmosphere used for the growth up tothe p-type AlGaN/GaN superlattice cap layer 19 after the growth of theactive layer 7 is the N₂ atmosphere and does not contain H₂, eliminationof In from the active layer 7 is prevented, and the active layer 7 isprevented from deterioration. Additionally, the carrier gas atmosphereused for the growth of the p-type GaN optical guide layer 10, p-typeAlGaN/GaN superlattice clad layer 18 and p-type GaN contact layer 12 isthe mixed gas atmosphere containing N₂ and H₂, these p-type layers canbe grown in a good crystalline quality.

According to the tenth embodiment, since the semiconductor laser isconfigured such that the active layer 7, undoped InGaN deteriorationpreventing layer 8, undoped GaN optical guide layer 17, p-type AlGaN/GaNsuperlattice cap layer 19, p-type GaN optical guide layer 10 and p-typeAlGaN/GaN superlattice clad layer 18 and sequentially lie in contact andthe undoped GaN optical guide layer 17 is as thin as 20˜40 nm, the sameadvantages as those of the fifth embodiment can be obtained.Additionally, since the undoped InGaN deterioration preventing layer 8is formed adjacent to the active layer 7, the same advantages as thoseof the first embodiment are obtained.

Next explained is a GaN compound semiconductor laser according to theeleventh embodiment of the invention. FIG. 15 is an energy band diagramof this GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the eleventhembodiment, the undoped GaN optical guide layer 17 is formed in contactwith the active layer 7; the p-type AlGaN/GaN superlattice cap layer 19is formed in contact with the undoped GaN optical guide layer 17; andthe p-type AlGaN/GaN superlattice clad layer 18 is formed in contactwith the p-type AlGaN/GaN superlattice cap layer 19. In the otherrespects, the structure of the laser shown here is identical to those ofthe GaN compound semiconductor lasers according to the first, fifth andninth embodiments. So, its explanation is omitted here.

This GaN compound semiconductor laser can be manufactured by essentiallythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment. In this embodiment, however, thefollowing special conditions are used for growth temperature and carriergas when growing individual layers. For example, growth temperature isset at 1000° C. for growth of layers from the undoped GaN layer 3 to then-type AlGaN clad layer 5, at 800° C. for growth of layers from then-type GaN optical guide layer 6 to the p-type AlGaN/GaN superlatticecap layer 19, and at 1000° C. for growth of layers from the p-type GaNoptical guide layer 10 to the p-type GaN contact layer 12. As to carriergas, a mixed gas atmosphere containing N₂ and H₂ is used for growth oflayers from the undoped GaN layer 3 to the n-type AlGaN clad layer 5, aN₂ atmosphere is used for growth of layers from the n-type GaN opticalguide layer 6 to the p-type AlGaN/GaN superlattice cap layer 19, and amixed gas atmosphere containing N₂ and H₂ is used for growth of layersfrom the p-type GaN optical guide layer 10 to the p-type GaN contactlayer 12. In this case, since the carrier gas atmosphere used for thegrowth up to the p-type AlGaN/GaN superlattice cap layer 19 after thegrowth of the active layer 7 is the N₂ atmosphere and does not containH₂, elimination of In from the active layer 7 is prevented, and theactive layer 7 is prevented from deterioration. Additionally, thecarrier gas atmosphere used for the growth of the p-type AlGaN/GaNsuperlattice clad layer 18 and the p-type GaN contact layer 12 is themixed gas atmosphere containing N₂ and H₂, these p-type layers can begrown in a good crystalline quality.

According to the eleventh embodiment, since the semiconductor laser isconfigured such that the active layer 7, undoped GaN optical guide layer17, p-type AlGaN/GaN superlattice cap layer 19 and p-type AlGaN/GaNsuperlattice clad layer 18 sequentially lie in contact and the undopedGaN optical guide layer 17 is as thin as 20˜40 nm, the same advantagesas those of the fifth embodiment can be obtained.

Next explained is a GaN compound semiconductor laser according to thetwelfth embodiment of the invention. FIG. 16 is an energy band diagramof this GaN compound semiconductor laser.

In the GaN compound semiconductor laser according to the twelfthembodiment, the undoped InGaN deterioration preventing layer 8 is formedin contact with the active layer 7; the undoped GaN optical guide layer17 is formed in contact with the undoped InGaN deterioration preventinglayer 8; the p-type AlGaN/GaN superlattice cap layer 19 is formed incontact with the undoped GaN optical guide layer 17; and the p-typeAlGaN/GaN superlattice clad layer 18 is formed in contact with thep-type AlGaN/GaN superlattice cap layer 19. Indium composition in theundoped GaN optical guide layer 17 is equal to that of the secondembodiment. In the other respects, the structure of the laser shown hereis identical to those of the GaN compound semiconductor lasers accordingto the first, fifth and ninth embodiments. So, its explanation isomitted here.

This GaN compound semiconductor laser can be manufactured by essentiallythe same method as that of the GaN compound semiconductor laseraccording to the first embodiment. In this embodiment, however, thefollowing special conditions are used for growth temperature and carriergas when growing individual layers. For example, growth temperature isset at 1000° C. for growth of layers from the undoped GaN layer 3 to then-type AlGaN clad layer 5, at 800° C. for growth of layers from then-type GaN optical guide layer 6 to the undoped GaN deteriorationpreventing layer 8, at 880° C. for growth of the undoped GaN opticalguide layer 17 and the p-type AlGaN/GaN superlattice cap layer 19, andat 1000° C. for growth of layers from the p-type GaN optical guide layer10 to the p-type GaN contact layer 12. As to carrier gas, a mixed gasatmosphere containing N₂ and H₂ is used for growth of layers from theundoped GaN layer 3 to the n-type AlGaN clad layer 5, a N₂ atmosphere isused for growth of layers from the n-type GaN optical guide layer 6 tothe undoped GaN deterioration preventing layer 8, and a mixed gasatmosphere containing N₂ and H₂ is used for growth of the p-typeAlGaN/GaN superlattice clad layer 18 and the p-type GaN contact layer12. In this case, since the carrier gas atmosphere used for the growthup to the p-type AlGaN/GaN superlattice cap layer 19 after the growth ofthe active layer 7 is the N₂ atmosphere and does not contain H₂,elimination of In from the active layer 7 is prevented, and the activelayer 7 is prevented from deterioration. Additionally, the carrier gasatmosphere used for the growth of the p-type AlGaN/GaN superlattice cladlayer 18 and the p-type GaN contact layer 12 is the mixed gas atmospherecontaining N₂ and H₂, these p-type layers can be grown in a goodcrystalline quality.

According to the twelfth embodiment, since the semiconductor laser isconfigured such that the active layer 7, undoped GaN deteriorationpreventing layer 8, undoped GaN optical guide layer 17, p-type AlGaN/GaNsuperlattice cap layer 19 and p-type AlGaN/GaN superlattice clad layer18 sequentially lie in contact and the undoped GaN optical guide layer17 is as thin as 20˜40 nm, the same advantages as those of the fifthembodiment can be obtained. Additionally, since the undoped InGaNdeterioration preventing layer 8 is provided adjacent to the activelayer, the same advantages as those of the first embodiment areobtained.

Heretofore, embodiments of the invention have been explainedspecifically. However, the invention is not limited to those embodimentsbut contemplates various changes and modifications based on thetechnical concept of the invention.

For example, numerical values, structures, substrates, source materials,processes, and the like, specifically indicated in conjunction with thefirst to twelfth embodiments are not but examples, and any appropriatenumerical values, structures, substrates, source materials, processes,etc. may be used.

More specifically, for example, although the first to twelfthembodiments have been explained as first depositing n-type layers of thelaser structure on the substrate and thereafter depositing p-typelayers. However, the order of deposition may be opposite to firstdeposit p-type layers on the substrate and thereafter deposit n-typelayers.

Further, the first to twelfth embodiments use the c-plane sapphiresubstrate, but a SiC substrate, Si substrate or spinel substrate, forexample, may be used instead, where appropriate. Furthermore, an AlNbuffer layer or AlGaN buffer layer may be used instead of the GaN bufferlayer.

The first to twelfth embodiments have been explained as applying theinvention to the manufacture of a GaN compound semiconductor laser of aSCH structure. Instead, the invention is applicable to the manufactureof a GaN compound semiconductor laser of a DH structure (doubleheterostructure), for example, or to the manufacture of a GaN compoundlight emitting diode, or further to an electron transporting deviceusing nitride III-V compound semiconductors, such as GAN compound FET,GaN compound heterojunction bipolar transistor (HBT), for example.

The first and second embodiments have been explained as using H₂ gas asthe carrier gas for growth by MOCVD. However, any other appropriate gassuch as a mixed gas of H₂ and N₂, or with He or Ar gas.

As described above, according to the invention, since an intermediatelayer of a second nitride III-V compound semiconductor containing In andGa but different from a first nitride III-V compound semiconductor isprovided in contact with an active layer of the first nitride III-Vcompound semiconductor containing In and Ga or a layer of the firstnitride III-V compound semiconductor, the intermediate layersignificantly alleviates the stress produced in the active layer or thelayer of the first nitride III-V compound semiconductor by a cap layer,or the like, or effectively prevents diffusion of Mg used as a p-typedopant of p-type layers into the active layer or the layer of nitrideIII-V compound semiconductor. Thereby, the invention can realize asemiconductor device using nitride III-V compound semiconductors, whichis sufficiently reduced in initial deterioration rate, elongated inlifetime, remarkably reduced in change of the operation current withtime, and remarkably reduced in emission unevenness. Such asemiconductor device, which may be a semiconductor light emittingdevice, can be manufactured easily by the manufacturing method accordingto the invention.

Additionally, by optimizing the position of the cap layer, the opticalguide layer or the first optical guide layer can be grown in a goodcrystalline quality as compared with a structure locating the cap layeradjacent to the active layer with or without interposing theintermediate layer, or the optical guide layer or the first opticalguide layer can be optimized in thickness. Therefore, it is possible torealize a semiconductor light emitting device made of nitride III-Vcompound semiconductors, which is elongated in life, enhanced insymmetry of intensity distribution of light in far-field imagesespecially in case of a semiconductor laser and improved in aspect ratioof the radiation angle, or a semiconductor device made of nitride III-Vcompound semiconductors, which is elongated in lifetime. Such asemiconductor light emitting device or semiconductor device can bemanufactured easily by the manufacturing method according to theinvention.

1. A semiconductor light emitting device comprising: an active layermade of a first nitride III-V compound semiconductor containing In andGa; an optical guide layer in contact with the active layer and made ofa second nitride III-V compound semiconductor containing Ga; a cap layerin contact with the optical guide layer and made of a third nitrideIII-V compound semiconductor containing Al and Ga; and a p-type cladlayer in contact with the cap layer and made of a fourth nitride III-Vcompound semiconductor containing Al and Ga and different from the thirdnitride III-V compound semiconductor, wherein, the p-type clad layercomposes a superlattice clad layer and is effective to confine lightfrom the active layer, and the cap layer at all points has a band gaplarger than that of the p-type clad layer, and the thickness of the caplayer is equal to or more than 2 nm and equal to or less than 20 nm. 2.The semiconductor light emitting device according to claim 1 wherein thethird nitride III-V compound semiconductor composing the cap layer isAl_(y)Ga_(1-y)N (where 0≦y<1).
 3. The semiconductor light emittingdevice according to claim 1 wherein the optical guide layer is undoped.4. The semiconductor light emitting device according to claim 1 whereinthickness of the optical guide layer is equal to or more than 8 nm. 5.The semiconductor light emitting device according to claim 1 wherein thesuperlattice clad layer comprises alternately stacking AlGaN and GaNlayers.
 6. A semiconductor light emitting device comprising: an activelayer made of a first nitride III-V compound semiconductor containing Inand Ga; an optical guide layer in contact with the active layer and madeof a second nitride III-V compound semiconductor containing Ga; a caplayer in contact with the optical guide layer and made of a thirdnitride III-V compound semiconductor containing Al and Ga; and a p-typeclad layer in contact with the cap layer and made of a fourth nitrideIII-V compound semiconductor containing Al and Ga and different from thethird nitride III-V compound semiconductor; wherein, the p-type cladlayer is effective to confine light from the active layer, and the caplayer at all points has a band gap that is larger than that of thep-type clad layer, and the thickness of the cap layer is equal to ormore than 2 nm and equal to or less than 20 nm.
 7. The semiconductorlight emitting device according to claim 6 wherein the third nitrideIII-V compound semiconductor composing the cap layer is Al_(y)Ga_(1-y)N(where 0≦y<1).
 8. The semiconductor light emitting device according toclaim 6 wherein the optical guide layer is undoped.
 9. The semiconductorlight emitting device according to claim 6 wherein thickness of theoptical guide layer is equal to or more than 8 nm.
 10. A semiconductorlight emitting device comprising: an active layer made of a firstnitride III-V compound semiconductor containing In and Ga; an opticalguide layer in contact with the active layer and made of a secondnitride III-V compound semiconductor containing Ga; a cap layer incontact with the optical guide layer and made of a third nitride III-Vcompound semiconductor containing Al and Ga; and a p-type clad layer incontact with the cap layer and made of a fourth nitride III-V compoundsemiconductor containing Al and Ga and different from the third nitrideIII-V compound semiconductor, wherein, the p-type clad layer is notcontinuously graded and is effective to confine light from the activelayer, and the cap layer at all points has a band gap larger than thatof the p-type clad layer, the thickness of the cap layer is equal to ormore than 2 nm and equal to or less than 20 nm.
 11. The semiconductorlight emitting device according to claim 10 wherein the third nitrideIII-V compound semiconductor composing the cap layer is Al_(y)Ga_(1-y)N(where 0≦y<1).
 12. The semiconductor light emitting device according toclaim 10 wherein the optical guide layer is undoped.
 13. Thesemiconductor light emitting device according to claim 10 whereinthickness of the optical guide layer is equal to or more than 8 nm. 14.A semiconductor light emitting device comprising: an active layer madeof a first nitride III-V compound semiconductor containing In and Ga; anoptical guide layer in contact with the active layer and made of asecond nitride III-V compound semiconductor containing Ga; a cap layerin contact with the optical guide layer and made of a third nitrideIII-V compound semiconductor containing Al and Ga; and a p-type cladlayer in contact with the cap layer and made of a fourth nitride III-Vcompound semiconductor containing Al and Ga and different from the thirdnitride III-V compound semiconductor, wherein the p-type clad layercomprises one or more discrete electron energy levels and is effectiveto confine light from the active layer, and the cap layer at all pointshas a band gap larger than that of the p-type clad layer, and thethickness of the cap layer is equal to or more than 2 nm and equal to orless than 20 nm.
 15. The semiconductor light emitting device accordingto claim 14 wherein the third nitride III-V compound semiconductorcomposing the cap layer is Al_(y)Ga_(1-y)N (where 0≦y<1).
 16. Thesemiconductor light emitting device according to claim 14 wherein theoptical guide layer is undoped.
 17. The semiconductor light emittingdevice according to claim 14 wherein thickness of the optical guidelayer is equal to or more than 8 nm.
 18. The semiconductor lightemitting device according to claim 14 wherein each of the discreteelectron energy levels is less than an energy level for the cap layer.